This invention relates to a door lock.
In locks of the type in which a lock bolt is retracted by operating a handle to retract a slide carriage which carries the bolt, various methods have been employed to prevent retraction of the slide carriage until the lock is operated by an appropriate key. In one such method use of the key causes a plate piece to rotate resulting in engagement of notches in the front end of the plate piece with the slide carriage. In another such method, the key acts via a linkage to raise a blocking plate which is located between the rear end of the slide carriage and the rear wall of the lock case.
These conventional locks suffer the disadvantage that if an instrument such as a pipe wrench is used to forcibly turn the handle, the lock's security is impaired since the mechanism may be broken.